Try to use Fog credentials if no config file is provided

It seemed it would be nice to not have to provide, or specify, the config/ec2.yml file since that information is often going to be duplicated in the ~/.fog file anyway.  If CapifyEc2 fails to load the yaml config then it will try to use the Fog credentials.

I am open to suggestions for what the default region should be.  Since Fog defaults to us-east-1 that's what I used.

The pull request also contains an update to the current version of Fog.  I haven't tested it with the older version, but I believe that it should work since I'm only using Fog.credentials and not any of the actual api.